Hybrid fan blade biscuit construction

ABSTRACT

An airfoil for a gas turbine engine is disclosed. The airfoil may include a first portion including a first slot, a second portion including a second slot, and a biscuit disposed within the first slot and the second slot. The first portion and the second portion may be joined by the biscuit. A method for constructing an airfoil is also disclosed. The method may include making a first slot on a sheath, the first slot sized to fit a first part of a biscuit; making a second slot on a body, the second slot sized to fit a second part of the biscuit; and joining the sheath and the body together through a biscuit joint, the biscuit disposed within the first slot and the second slot.

CROSS-REFERENCE TO RELATED APPLICATION

This Application is a US National Stage under 35 USC § 371 ofInternational Patent Application No. PCT/US13/75356 filed on Dec. 16,2013, and claims priority under 35 USC § 119(e) to U.S. ProvisionalPatent Application Ser. No. 61/791,108 filed on Mar. 15, 2013 and61/855,574 filed on Oct. 2, 2013.

FIELD OF THE DISCLOSURE

The present disclosure relates generally to gas turbine engines and,more particularly, to fan blades in a gas turbine engine.

BACKGROUND OF THE DISCLOSURE

Gas turbine engines may typically include a fan, a compressor, acombustor, and a turbine, with an annular flow path extending axiallythrough each. Initially, the fan, which is powered by the turbine, drawsambient air into the engine. Part of the air flows through thecompressor where it is compressed or pressurized. The combustor thenmixes and ignites the compressed air with fuel, generating hotcombustion gases. These hot combustion gases are then directed from thecombustor to the turbine where power is extracted from the hot gases bycausing blades of the turbine to rotate. The other part of the airflowfrom the fan is used to generate forward thrust.

Various components of the gas turbine engine, such as fan, compressor,and turbine airfoils, are subject to the impact of foreign objects. Forexample, fan blades may experience foreign object damage (FOD) fromdebris or birds, which may reduce the life of the fan blades.Accordingly, there exists a need for an airfoil design with reinforcedstrength and impact tolerance.

Furthermore, when increasing the strength of airfoils, there are addedconcerns of increased weight and thickness, which may decrease theaerodynamic performance of the airfoils and gas turbine engine as awhole. Therefore, there exists a need for an impact resistant airfoilthat is also lightweight and aerodynamic. This disclosure is directed tosolving these needs and others.

SUMMARY OF THE DISCLOSURE

According to one embodiment, an airfoil for a gas turbine engine isdisclosed. The airfoil may comprise a first portion including a firstslot, a second portion including a second slot, and a biscuit disposedwithin the first slot and the second slot. The first portion and thesecond portion may be joined by the biscuit.

In a refinement, the first portion may be a sheath and the secondportion may be a body.

In a related refinement, the body may be hollow.

In another refinement, the biscuit may be positioned near a leadingedge.

In a refinement, the biscuit may be positioned in an outer span.

In another refinement, the biscuit may be composed of organic compositematerial.

In a refinement, the biscuit may be composed of energy absorbentmaterial.

In another refinement, the biscuit may be composed of Kevlar.

In yet another refinement, at least one of the first portion and thesecond portion may be bonded to the biscuit.

According to another embodiment, a gas turbine engine is disclosed. Thegas turbine engine may comprise a fan section, a compressor sectiondownstream of the fan section, a combustor section downstream of thecompressor section, and a turbine section downstream of the combustorsection. At least one of the fan section, compressor section, and theturbine section having an airfoil may include a sheath including a firstslot sized to fit a first part of a biscuit, a body including a secondslot sized to fit a second part of the biscuit, and a biscuit jointbetween the sheath and the body. The biscuit joint may include a biscuitdisposed within and bonded to the first and second slots. The sheath andthe body may be joined together by the biscuit.

In a refinement, the biscuit may be positioned near a leading edge ofthe airfoil.

In a related refinement, the biscuit may be positioned in an outer spanof the airfoil.

In another refinement, the biscuit may be composed of ballisticmaterial.

In a refinement, a material of the biscuit may be of lighter weight thana material of the sheath, and the material of the biscuit may be oflighter weight than a material of the body.

In another refinement, the biscuit may increase stiffness, impactresistance, and aerodynamic performance of the airfoil.

According to yet another embodiment, a method for constructing anairfoil is disclosed. The method may comprise making a first slot on asheath, the first slot sized to fit a first part of a biscuit. Themethod may further comprise making a second slot on a body, the secondslot sized to fit a second part of the biscuit. The method may furthercomprise joining the sheath and the body together through a biscuitjoint, the biscuit disposed within the first slot and the second slot.

In a refinement, the method may further comprise bonding the biscuit tothe first slot.

In another refinement, the method may further comprise bonding thebiscuit to the second slot.

In another refinement, the method may further comprise positioning thefirst slot, the second slot, and the biscuit near a leading edge and anouter span of the airfoil.

In yet another refinement, the method may further comprise composing thebiscuit of organic composite material.

These and other aspects and features of the disclosure will become morereadily apparent upon reading the following detailed description whentaken in conjunction with the accompanying drawings. Although variousfeatures are disclosed in relation to specific exemplary embodiments ofthe invention, it is understood that the various features may becombined with each other, or used alone, with any of the variousexemplary embodiments of the invention without departing from the scopeof the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a gas turbine engine, according toan embodiment of the present disclosure;

FIG. 2 is a side view of an airfoil in the gas turbine engine of FIG. 1;

FIG. 3 is a top down view of the airfoil of FIG. 2;

FIG. 4 is a side view of a sheath of the airfoil of FIG. 2;

FIG. 5 is a side view of a body of the airfoil of FIG. 2;

FIG. 6 is a side view of a biscuit of the airfoil of FIG. 2;

FIG. 7 is a side view of an airfoil, according to another embodiment ofthe present disclosure;

FIG. 8 is a top down view of the airfoil of FIG. 7; and

FIG. 9 is a flowchart illustrating an exemplary process for constructingan airfoil for a gas turbine engine, according to another embodiment ofthe present disclosure.

While the present disclosure is susceptible to various modifications andalternative constructions, certain illustrative embodiments thereof willbe shown and described below in detail. The invention is not limited tothe specific embodiments disclosed, but instead includes allmodifications, alternative constructions, and equivalents thereof.

DETAILED DESCRIPTION

Referring now to the drawings, and with specific reference to FIG. 1, inaccordance with the teachings of the disclosure, an exemplary gasturbine engine 20 is shown. The gas turbine engine 20 may generallycomprise a fan section 22 which draws ambient air into the engine 20, acompressor section 24 where air is pressurized, a combustor 26downstream of the compressor section which mixes and ignites thecompressed air with fuel and thereby generates hot combustion gases, aturbine section 28 downstream of the combustor 26 for extracting powerfrom the hot combustion gases, and an annular flow path 30 extendingaxially through each. Gas turbine engine 20 may be used on an aircraftfor generating thrust or power, or in land-based operations forgenerating power as well.

Turning now to FIGS. 2-6, an airfoil 40 of the gas turbine engine 20 isshown, according to an embodiment of the present disclosure. The airfoil40 may comprise a fan blade in the fan section 22, or a rotor blade orstator vane in the compressor section 24 or turbine section 28 of thegas turbine engine 20. Airfoil 40 may project radially from an end wallof a rotor in the engine 20. The airfoil 40 may include a first side 42and an opposite second side 44 extending axially from a leading edge 46to a trailing edge 47 (downstream of the leading edge 46) and extendingradially from a base 48 to a tip 50.

Airfoil 40 may be of a hybrid construction including a first portion orsheath 52 and a second portion or body 54. The sheath 52 may generallycomprise the leading edge 46 and extend a distance therefrom. Composedof solid titanium, or other suitable materials, the sheath 52 mayprovide impact tolerance to foreign object damage (FOD). The body 54 maygenerally comprise a majority of the airfoil 40, extending from thesheath 52 to the trailing edge 47, although other configurations arecertainly possible. The body 54 may be composed of an aluminum alloy, orother suitable materials.

The sheath 52 and body 54 may be joined together through a biscuit joint56. The biscuit joint 56 may include a biscuit 58 composed of a stiff,lightweight material that absorbs energy from an impact and increases astiffness, impact resistance, and aerodynamic performance of the airfoil40. The biscuit 58 may be composed of a material that is of lighterweight than a material of the sheath 52 and is of lighter weight than amaterial of the body 54. For example, the biscuit 58 may be composed ofan organic composite material (e.g., carbon fibers) or organic matrixcomposites, polymer matrix composite material, energy absorbentmaterial, ballistic material, synthetic material (e.g., para-aramidsynthetic fiber), Kevlar® (poly-paraphenylene terephthalamide), or thelike. By using stiff, lightweight material, the biscuit 58 increases theimpact tolerance capabilities of the airfoil 40, while decreasing aweight and thickness of the airfoil 40. Although the biscuit 58 may becomposed of lightweight material that absorbs energy from an impact,other materials, such as stiff metals (e.g., steel or nickel alloys) maybe used.

The sheath 52 may include a first slot 60 sized to fit a first part 62of the biscuit 58, and the body 54 may include a second slot 64 sized tofit a second part 66 of the biscuit 58. As shown best in FIG. 3, thefirst slot 60 of the sheath 52 may include a recess 68 and flankportions 70 to receive the first part 62 of the biscuit 58. Similarly,the second slot 64 may include a recess 72 and flank portions 74 toreceive the second part 66 of the biscuit 58.

Disposed within the first and second slots 60, 64, the biscuit 58provides a common element of attachment for both the sheath 52 and body54. With the first part 62 of the biscuit 58 disposed within the firstslot 60 of the sheath 52 and the second part 66 of the biscuit 58disposed within the second slot 64 of the body 54, the sheath 52 andbody 54 may be compressed together about the biscuit 58. Surface 76 ofthe sheath 52 and surface 78 of the body 54 abut against each other,forming a press fit relationship with the biscuit 58.

The sheath 52 and body 54 may be bonded to the biscuit 58. For example,an epoxy, polyurethane adhesive, or other structural adhesive may beused to bond the sheath 52 and body 54 to the biscuit 58. The first part62 of the biscuit 58 may be bonded to the first slot 60 of the sheath52, and the second part 66 of the biscuit 58 may be bonded to the secondslot 64 of the body 54. The first and second slots 60, 64 may providerequisite surface area for bonding to the biscuit 58. Furthermore, anepoxy, polyurethane adhesive, or other structural adhesive may be usedto bond the sheath 52 to the body 54 where surfaces 76, 78 of the sheath52 and body 54 are in contact with each other. It is to be understoodthat other methods may be used to bond the biscuit 58, sheath 52, andbody 54 together in a biscuit joint 56, such as, without limitation,welding or the like. The biscuit 58, sheath 52, and body 54 may also bejoined together via fasteners (e.g., rivets, screws, bolts, etc.),mechanical retention (e.g., inserts, rails, etc.), or other methods.

The biscuit 58 (and associated slots 60, 64 in the sheath 52 and body54) may be positioned near the leading edge 46 and in an outer span ofthe airfoil 40. As used herein, the term “span” refers to a length S ofthe airfoil 40 from the base 48 to the tip 50, with relevant distancesexpressed as a percentage of the length S (0% referenced at the base 48and 100% referenced at the tip 50). The outer span of the airfoil 40includes a range of about 50% to about 100% of the length S of the spanof the airfoil 40. The position of the biscuit 58 near the leading edge46 and in the outer span helps stiffen the airfoil 40 and enhance impacttolerance capabilities, while maintaining a minimal thickness of theairfoil 40 in the outer span. The biscuit 58 may also provide internalmechanical damping to the airfoil 40 in order to reduce vibratory stresslevels and enhance distortion tolerance capabilities.

It is to be understood that, although not shown, the biscuit 58 may alsobe positioned near the trailing edge 47 and/or any location between theleading and trailing edges 46, 47, as well as in an inner span (a rangeof about 0% to about 50% of the length S of the span) of the airfoil 40and/or any location between the base 48 and tip 50. In addition, othershapes for the biscuit 58 and arrangements for the biscuit joint 56 thanthat shown and described are certainly possible. For example, more thanone biscuit 58 or more than one biscuit joint 56 may be used to joinvarious parts of the airfoil 40 together.

Although the airfoil 40, shown in FIGS. 2-6, is of a solid construction,in another embodiment shown best in FIGS. 7-8, the airfoil 40 may be ofa hollow construction. The airfoil 40 may have one or more cavities 80in order to decrease a weight of the airfoil 40, thereby increasing theaerodynamic performance of the airfoil 40. It is to be understood thatthe biscuit joint 56 may be used in other configurations of airfoilsthan that shown and described herein.

Referring now to the flowchart of FIG. 9, with continued reference toFIGS. 1-8, an exemplary process 90 for constructing an airfoil 40 for agas turbine engine 20 is shown. At block 92, the first slot 60 may bemade on the sheath 52, the first slot 60 sized to fit the first part 62of the biscuit 58. At block 94, the second slot 64 may be made on thebody 54, the second slot 64 sized to fit the second part 66 of thebiscuit 58. For example, the first and second slots 60, 64 may be madein the sheath 52 and body 54, respectively, via machining, standardmilling, electrical discharge machining, electrochemical machining,chemical milling, forming material into shape (e.g., bending), or thelike. At block 96, the sheath 52 and the body 54 may be joined togetherthrough the biscuit joint 56 with the biscuit 58 positioned within thefirst slot 60 and the second slot 64. For example, the biscuit 58 may bebonded or welded to the first slot 60 of the sheath 52 and the secondslot 64 of the body 54. It is to be understood that blocks 92-96 may beperformed in a different order than that shown in FIG. 9.

INDUSTRIAL APPLICABILITY

From the foregoing, it can be seen that the teachings of this disclosurecan find industrial application in any number of different situations,including but not limited to, gas turbine engines. Such engines may beused, for example, on aircraft for generating thrust, or in land,marine, or aircraft applications for generating power.

The present disclosure provides a hybrid airfoil biscuit constructionfor a gas turbine engine and a method of manufacturing same. Thedisclosed biscuit joint for the airfoil serves the dual purpose ofjoining the sheath to the body and enhancing impact tolerancecapabilities of the airfoil. By providing a biscuit as a common point ofattachment for the sheath and the body, a strong joint between thesheath and the body may be achieved. In addition, by selectinglightweight, energy absorbent materials for the biscuit, the biscuitjoint reinforces the strength and stiffness of the airfoil, whiledecreasing its weight and thickness.

Placing the biscuit near the leading edge and outer span of the airfoilfurther improves the impact resistance of the airfoil to FOD. Thebiscuit may also provide internal mechanical damping to the airfoil inorder to reduce vibratory stress levels and enhance distortion tolerancecapabilities. Thus, the disclosed hybrid airfoil biscuit constructionprovides a robust, durable, and aerodynamic airfoil for a gas turbineengine, which thereby increases the life and aerodynamic performance forthe gas turbine engine as a whole.

While the foregoing detailed description has been given and providedwith respect to certain specific embodiments, it is to be understoodthat the scope of the disclosure should not be limited to suchembodiments, but that the same are provided simply for enablement andbest mode purposes. The breadth and spirit of the present disclosure isbroader than the embodiments specifically disclosed, and includes allembodiments and equivalents encompassed within the claims appendedhereto as well.

What is claimed is:
 1. An airfoil for a gas turbine engine, comprising:a first portion including a first slot; a second portion including asecond slot, wherein the first portion and the second portion are joinedtogether by a biscuit joint comprising a biscuit disposed within thefirst slot and the second slot, wherein the first portion is a sheathlocated on a leading edge of the airfoil, the first slot being definedby flank portions of the sheath extending on opposite sides of theairfoil proximate to the leading edge and the second slot is defined byflank portions of the airfoil extending on opposite sides of the airfoilproximate to the leading edge, wherein the first slot and the secondslot extend along a span of the airfoil, wherein the biscuit has a firstend located proximate to a tip of the airfoil and a second end locatedproximate to a mid-span of the airfoil, and wherein the biscuit extendsfurther into the second slot than the first slot.
 2. The airfoil ofclaim 1, wherein a body of the airfoil is hollow.
 3. The airfoil ofclaim 1, wherein the biscuit is positioned in an outer span of theairfoil and the outer span includes a range of about 50% to 100% of alength of the span of the airfoil.
 4. The airfoil of claim 1, whereinthe biscuit is composed of organic composite material.
 5. The airfoil ofclaim 1, wherein the biscuit is composed of energy absorbent material.6. The airfoil of claim 1, wherein the biscuit is composed ofpoly-paraphenylene terephthalamide.
 7. The airfoil of claim 1, whereinat least one of the sheath and the second portion is bonded to thebiscuit.
 8. A gas turbine engine, comprising: a fan section; acompressor section downstream of the fan section; a combustor sectiondownstream of the compressor section; and a turbine section downstreamof the combustor section, at least one of the fan section, compressorsection, and the turbine section having an airfoil including: a sheathincluding a first slot sized to fit a first part of a biscuit, a body ofthe airfoil including a second slot sized to fit a second part of thebiscuit, and a biscuit joint between the sheath and the body, thebiscuit joint including a biscuit disposed within and bonded to thefirst and second slots, the sheath and the body joined together by thebiscuit, wherein the first slot is defined by flank portions of thesheath extending on opposite sides of the airfoil and the second slot isdefined by flank portions of the body of the airfoil extending onopposite sides of the airfoil, wherein the sheath is located on aleading edge of the airfoil, and wherein the first slot and the secondslot extend along a span of the airfoil, wherein the biscuit has a firstend located proximate to a tip of the airfoil and a second end locatedproximate to a mid-span of the airfoil, and wherein the biscuit extendsfurther into the second slot than the first slot.
 9. The gas turbineengine of claim 8, wherein the biscuit is positioned in an outer span ofthe airfoil and the outer span includes a range of about 50% to 100% ofa length of the span of the airfoil.
 10. The gas turbine engine of claim8, wherein the biscuit is composed of ballistic material.
 11. The gasturbine engine of claim 8, wherein a material of the biscuit is oflighter weight than a material of the sheath, and wherein the materialof the biscuit is of lighter weight than a material of the body.
 12. Thegas turbine engine of claim 8, wherein the biscuit increases stiffness,impact resistance, and aerodynamic performance of the airfoil.
 13. Amethod for constructing an airfoil, comprising: making a first slot on asheath, the first slot sized to fit a first part of a biscuit; making asecond slot on a body of the airfoil, the second slot sized to fit asecond part of the biscuit, wherein the first slot is defined by flankportions of the sheath extending on opposite sides of the airfoil andthe second slot is defined by flank portions of the body of the airfoilextending on opposite sides of the airfoil; and joining the sheath andthe body together at a leading edge of the airfoil through a biscuitjoint, the biscuit disposed within the first slot and the second slot,wherein the first slot and the second slot extend along a span of theairfoil, wherein the biscuit has a first end located proximate to a tipof the airfoil and a second end located proximate to a mid-span of theairfoil, and wherein the biscuit extends further into the second slotthan the first slot.
 14. The method of claim 13, further comprisingbonding the biscuit to the first slot.
 15. The method of claim 13,further comprising bonding the biscuit to the second slot.
 16. Themethod of claim 13, further comprising positioning the first slot, thesecond slot, and the biscuit at an outer span of the airfoil wherein theouter span includes a range of about 50% to 100% of a length of the spanof the airfoil.
 17. The method of claim 13, further comprising composingthe biscuit of organic composite material.